seabirds lecture 10. common groupings of marine birds seabirds—e.g. penguins, pelicans, gulls,...
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SeabirdsLecture 10
Common Groupings of Marine Birds• Seabirds—e.g. penguins, pelicans, gulls, terns– Capable of feeding away from shore– Breed on islands or coastal zones
• Shorebirds—e.g. sandpipers– Feed on shorelines in sand/mud
• Wading birds—e.g. herons, egrets– Freshwater or marine– Marsh birds– Hunters
Seabird Diversity• 27 orders of birds—10,000 species– Four contain “true” seabirds
• Sphenisciformes—Penguins • Procellariformes—Albatrosses, Petrels• Pelecaniformes—Pelicans, Cormorants• Charadriiformes—Gulls, Terns
Representative Families
Family Sternidae: Terns—45 species• Slender, rapid wings• Smaller than gulls• Broad tail, often V-shaped• Feed on fish at surface• Many species highly migratory Royal Tern
Representative Families
Family Laridae: Gulls—56 species• Intelligent – Often adaptable to human
disturbance• Generalist carnivores– The least specialized of all seabirds
• More generalized morphology
Laughing Gull
Representative Families
Family Pelecanidae: Pelicans— 8 species
• Feed on fish at surface– Gular pouch on lower jaw
• One of the heaviest flying birds– Brown pelican is smallest species
Brown Pelican
Life History—Nesting • Generally occurs at inaccessible coastal areas– Isolated islands, cliff faces, coastal wetlands• Two reasons—
– Large nesting colonies– Adults return to natal area– Both parents involved with care
Life History—Offspring • Egg incubation 25-35 days• Fledging period 1-2 months• Juvenile seabirds often different plumage color– 4-5 years until maturity
Royal Tern Creche
Seabird Foraging—Gulls• Unhinging jaws—• Take live prey– Tool use• Baiting, breaking shells
– Plunge diving• Scavenging—• Kleptoparasitism—• Advantages of walking
ability?
Spring Summer Fall
% o
f die
t
Starfish
Mussels Crabs
Herring GullDutch Colony
Seabird Foraging—Terns & Pelicans• Plunge diving—pelicans
• Only two species dive• Impact on left side—• Impact may stun fish
– Pelicans may also feed from surface
– Air sacs beneath skin and in certain bones—
• Plunge diving—terns – Hovering
• Scavenging
Seabird Foraging—Terns
Seabird Foraging—other methodsNorthern Gannet
Dive from up to 100’Depth of up to 50’
Swim with wings/feet
Seabird Foraging—other methodsWilson’s Storm Petrel
Most abundant birdFeeds on inverts and small fish
Seabird Plumage Coloration• Generally drab coloration– White, black, gray, brown– Often countershaded
• Adaptive significance poorly studied—hypotheses?
• Wings shaped like airfoils— – Secondary feathers lift
• Primary feathers generate power—forward motion– Greater flexibility of motion• Connect to “hand” bones
– Large range of motion
Wing cross-section
Lift
Bird Wings—overview
Seabird Wings—high aspect ratio
Albatross
Grouse
Tern
Vulture
• Seabird wings not “slotted” to reduce drag• Extended secondary region increases lift• High apect ratio• Good for soaring (gliding)• Drawbacks?
Seabird Wings—high aspect ratio
Dynamic Soaring
Seabird Wings—High-speed wings
Albatross
Grouse
Tern
Vulture
• Streamlined• Greater proportion primary feathers• Good for sustained, high-speed flying• Hovering
• Energetically expensive
Seabird Osmoregulation• Nitrogenous waste Uric acid– Effective kidneys
• Salt Gland—• Many seabirds still require some freshwater• Pelagic seabirds months to years at sea
Seabird Conservation
• Loss of nesting habitat– Increased disturbance– Invasive species—nest predation– Oil spills
Seabird Conservation• Interactions with fishing gear– Long lines– Gill nets– Recreational entanglements
• Plastic pollution in ocean
Seabird Conservation—Success stories
Brown Pelican– Listed as endangered—1970• Delisted 2009
– DDT outlawed in 1972
Laughing Gulls• Nearly extirpated in U.S.• Late 1800s
• Plume hunters
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